“Time Machine”, all of you might have heard this word at least once in your life time, if not the word itself suggests the meaning. Till now it was in the virtual world (world in which a lot of “technical, hypothetical” things are being tested). But the news that an experiment at the European Organisation for Nuclear Research (CERN), the giant particle accelerator near Geneva, has obtained results at odds with Albert Einstein’s theory of relativity has the scientific world abuzz with consternation.Could the great Einstein have been wrong?
Einstein is one of the most revered figures in science. As every schoolboy knows, he came up with the formula ‘E=mc2 ’ where E stands for energy, m for mass and c for the speed of light in empty space. Known as mass energy equivalence, E=mc2 is what underpins energy production in nuclear power plants; it explains how the Sun and other stars produce light, and why atom bombs are so devastating.
In 1905, Einstein also postulated that the speed of light – approximately 3,00,000 kilometres per second – was the ultimate speed limit in the universe. Nothing could exceed it. In fact, if one were able to do so, all sorts of strange things would happen. Time would flow backwards. You could leave on a faster-than-light journey one morning and return the previous evening. Your weight would be negative. Time travel would be possible. To prevent these seeming absurdities, Einstein disallowed any speed faster than the speed of light.
Over the years, some people (mostly crackpots) have tried to prove that Einstein was wrong and it is possible to travel faster than the speed of light. But no experimental data have borne out this possibility – until now.
The CERN physicists who noted the discrepancy with Einstein were part of a team called OPERA. Their experiment produced neutrinos, ghostly and electrically neutral particles that are byproducts of nuclear reactions. Neutrinos very rarely interact with other matter; only occasionally can we detect their presence. The CERN physicists fired a beam of neutrinos from Geneva to an underground cavern in Gran Sasso in Italy, where a giant detector monitors
neutrinos. Over three years, they tracked some 15,000 neutrinos.
Here’s what perplexed them. The neutrinos from CERN were reaching the detector at Gran Sasso 90 nanoseconds (a nanosecond is one-billionth of a second) faster than light takes to cover the same distance. It was not a huge difference, but a difference nonetheless, and it was at odds with Einstein. They checked and rechecked their results, looking for obvious sources of experimental error, but couldn’t find anything that changed the results. So they let the world know what they had found.
Physicists everywhere are perplexed. While no one is prepared to jettison Einstein right away, a nagging doubt that Einstein might be proved wrong has been introduced.
If it does turn out that the neutrinos are travelling faster than light, it will be a big deal. The theory of relativity is the bedrock of modern physics. If it is proven inaccurate, all of modern physics will have to be reinterpreted. Textbooks will have to be rewritten. Everything in physics from cosmology (how the universe was created and how it behaved in the first few seconds) to nuclear medicine will have to be revised.
The real test of a scientific theory is its ability to make testable predictions. If experimental observations differ from what is predicted by theory, either the theory is wrong or incomplete. The history of science is full of examples of even very successful theories being overthrown because of experimental results.
Such was the case with the view of the universe espoused by the Greek philosopher Claudius Ptolemy in the second century. Ptolemy believed that the Earth was at the centre of the universe, and the sun, stars and planets revolved around it once a day. Ptolemy’s model seemed to work, and it found resonance in the Church’s world view. As such, it became the accepted model, holding sway for some 1,500 years. Yet, it was dead wrong. What finally overturned Ptolemaic astronomy were Galileo’s observations, coupled with the theories of Nicolaus Copernicus and Johannes Kepler.
Einstein himself benefited from an experiment that didn’t agree with conventional scientific wisdom in the 19th century. Back then, it was widely believed by physicists that light waves needed a medium to travel, just as sound waves need air or water. This medium came to be called the “luminiferous ether”. In the 1880s, Albert Michelson and Edward Morley set out to detect the ether. They reasoned that due to the Earth’s movement around the Sun and the Sun’s movement around the centre of the galaxy, the ether should be detected through a sensitive experiment that examined the speed of light in different directions. Yet, in spite of several attempts, Michelson and Morley found that the speed of light seemed the same whichever way they looked. This was a contradiction, and it implied there was no ether. In 1887, they published a paper to that effect, which motivated Einstein two decades later.
It is still too early to tell whether Einstein’s theory of relativity is wrong. The CERN experiments need to be independently verified. Since measuring neutrinos is so difficult, statistical methods were used by the OPERA team, and these methods are under careful investigation. There could also be some experimental error that was inadvertently overlooked.
In the coming days and months, the best brains in physics will scrutinise the CERN results and seek to independently verify them. At the end of the day, scientists know that if repeated experimental results do not agree with Einstein’s predictions, it is the experiments and not Einstein that will win.